CVE Vulnerabilities

CVE-2022-21949

Improper Restriction of XML External Entity Reference

Published: May 03, 2022 | Modified: May 10, 2022
CVSS 3.x
8.8
HIGH
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.x
9 HIGH
AV:N/AC:L/Au:S/C:C/I:C/A:C
RedHat/V2
RedHat/V3
Ubuntu
MEDIUM

A Improper Restriction of XML External Entity Reference vulnerability in SUSE Open Build Service allows remote attackers to reference external entities in certain operations. This can be used to gain information from the server that can be abused to escalate to Admin privileges on OBS. This issue affects: SUSE Open Build Service Open Build Service versions prior to 2.10.13.

Weakness

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

Affected Software

Name Vendor Start Version End Version
Open_build_service Opensuse * 2.10.13 (excluding)
Ruby-xmlhash Ubuntu bionic *
Ruby-xmlhash Ubuntu impish *
Ruby-xmlhash Ubuntu kinetic *
Ruby-xmlhash Ubuntu lunar *

Extended Description

XML documents optionally contain a Document Type Definition (DTD), which, among other features, enables the definition of XML entities. It is possible to define an entity by providing a substitution string in the form of a URI. The XML parser can access the contents of this URI and embed these contents back into the XML document for further processing. By submitting an XML file that defines an external entity with a file:// URI, an attacker can cause the processing application to read the contents of a local file. For example, a URI such as “file:///c:/winnt/win.ini” designates (in Windows) the file C:\Winnt\win.ini, or file:///etc/passwd designates the password file in Unix-based systems. Using URIs with other schemes such as http://, the attacker can force the application to make outgoing requests to servers that the attacker cannot reach directly, which can be used to bypass firewall restrictions or hide the source of attacks such as port scanning. Once the content of the URI is read, it is fed back into the application that is processing the XML. This application may echo back the data (e.g. in an error message), thereby exposing the file contents.

Potential Mitigations

References